Historically many types of combustion heads have been designed including flat heads, hemispherical (hemi-see Japanese Patent Pub. No. 52-54820, published May 4, 1977) and smoothed. The smoothed combustion chamber is disclosed in U.S. Pat. No. 5,941,221 (1999) to Marocco et al. His chamber is radiused and smoothed in order to reduce the surface area relative to the volume of the combustion chamber. His theory for improved efficiency is to increase the average combustion temperature, thereby producing more efficient combustion.
Many efforts to improve engine efficiency (horsepower) by means of maximizing airflow velocity have been made. U.S. Pat. No. 6,691,661 (2004) to Lundgreen et al. discloses a tuned air induction apparatus for a V-twin motorcycle engine. Separate intake passages for each cylinder allegedly improve airflow velocity and horsepower.
Nobody has invented a concave cylinder head which provides a straighter and shorter air passage in and out of the combustion chamber. The present invention reduces the air friction around the intake and exhaust valves by providing a straighter passage into and out of the combustion chamber. Engine performance is measurably increased by simply replacing a cylinder head with the present invention.